Public Lab Research note

Aerial Mapping of Effects of a Water Diversion

by section1group1 | May 30, 2017 16:23 30 May 16:23 | #14246 | #14246

Aerial Mapping of Effects of a Water Diversion

Choi, Doubleday, Everett, Kallett

A short way from our high school in Ojai, California is Thacher Creek. Much of it has been diverted to provide water for local agriculture and our school. Our school has rights to the water from 7 am Sunday to 7 am Monday, and from the period of time between April 10th to May 8th, our school pulled 810,000 gallons of water from the river. Assuming that the flow between Sunday and Monday is representative of the flow on other days of the week, we can estimate that in this a one-month period, the diversion has removed a total of 5.6 million gallons of water from the creek.

This huge sum obviously has impacts on the environment around it. A quick look on Google Earth or hikes on a trail along the creek demonstrate that. However, we really wanted to quantify the effects of the diversion, so we set about investigating methods of data collection that could give us a fuller picture of what's going on. We settled on aerial mapping, as photos from a great enough height can show the difference in vegetation. The amount of vegetation in an area can be a good indicator of if the area is receiving sufficient water and of the levels of biodiversity, and we were curious to know if the diversion had any effect on the levels of vegetation in that specific area.

For this aerial mapping project, we used the balloon mapping kit that is shown in this post: All it required was a balloon kit, helium, an empty plastic PET bottle and an ordinary point-and-shoot camera. We followed the instructions provided to cut the bottle into a casing and make a harness out of rubber bands. Then, we fixed the camera to the harness. Next, we filled the balloon with approximately 2000 psi of helium, attached the harness to the balloon, and sent the balloon up into the atmosphere.

We then compared the levels of foliage before the diversion and after the diversion in the photos to visually interpret our data. For our purposes, at least, this was all we needed to do. The differences were stark enough that we did not necessarily need to do further analysis. Below is one of our photos:

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Our conclusions are that the diversion significantly impacts the ecosystem, even more than we can see from the ground. The photographs showed a sharp contrast in the amount of vegetation in the creek before the diversion and after it. One side is lush and green while the other looks much more like the rest of the chaparral ecosystem.

Furthermore, the diversion creates a microclimate so distinct that different species of flora live on either side of it the diversion. Upstream, there are plenty of trees and broad-leafed shrubs, while downstream of the diversion there are more of the narrow-leafed, more drought-tolerant plants that are common in this part of Southern California.

Unfortunately, wind prohibited the balloon from flying higher and, accordingly, our photos only capture a small portion of the land surrounding the diversion. Our analysis could certainly be conclusive if we could see the same types of vegetation that we see before the diversion snaking upstream along the river.

Additionally, it is plausible that the effects of the diversion become much less pronounced in summer months. The river typically runs dry by June, and we presume that this would cause the flora before the diversion to start looking like the flora after the diversion.

For anyone who wants to continue with this type of project, we have put together several recommendations. First, fly your balloon as high as you can. This allows you a much broader, more expansive view of the land. A strong wind might prevent you from doing this, so try to do your transect on a calm day. In fact, we found that on a day with little wind, the camera rig(cut plastic bottle) is not even necessary.

Second, it is helpful to first explore the area on foot and on Google Earth to get a general sense of the type of vegetation in the area being mapped and the geography of the area. It is also helpful to secure a safe spot to fly the balloon beforehand to decrease the chances of a mishap.

Third, a set of spare batteries is essential. On our first flight, we hiked for half an hour out to the diversion only to find that our camera was dead. Don't let this happen to you.

Fourth, fly the balloon at a time of day when the sun is directly overhead. Shadows can make it much more difficult to interpret your data.

Fifth, protect the balloon. We popped two of them, both accidentally. One of the balloons was pushed into a nail by the wind, and another caught on a branch while returning from the transect. Regardless of how robust the balloon may seem, it is actually quite fragile and should be treated accordingly. We were lucky enough to have several spare balloons, but others may not be so fortunate.

This is a broader view of the diversion, but the orientation is flipped so that it is almost entirely rotated 90 degrees (as compared to the previous picture). The gray shaded area in the lower right-hand corner is a sheer rock face on the edge of the canyon, which is why there is no visible vegetation in that area.

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Here is a different view of the river area, with the black arrows showing where the river would be flowing if there was water. The red arrow also points out the white pipe that can be seen(and heard when standing nearby) that diverts the water from the river further up.

Below are photos of several other orientations and angles of the diversion. The sandy hill that appears to be dry and sparsely vegetated receives a lot of direct sunlight throughout the day, so its lack of vegetation is purely natural, rather than being caused by the diversion of the creek water.

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